Rotor apex seal damping device

ABSTRACT

A mechanism to damp vibration and chatter in the rotor apex seals of rotary internal combustion engines, pumps, compressors and other devices of generally epitrochoidal motion.

United States Patent 1 1 Gilbert 1March 20, 1973 [54] ROTOR APEX SEALDAMPING DEVICE [76] Inventor: William w. Gilbert, 372 SouthWilliamsburg, Birmingham, Mich. 48010 [22] Filed: June 25, 1971 [2]]App]. No.: 156,900

[52] U.S.Cl. ..4l8/ll3,418/115,418/123 [51] Int. Cl ..F01c 19/02, F03c3/00, F040 27/00 [58] Field ofSearch ..418/113,115,122-124; 227/81 P[56] References Cited UNITED STATES PATENTS 3,456,626 7/1969 Jones..413/115 3,213,837 10/1965 Keylwert r r ..418/122 3,366,317 l/l968Keylwert ....418/l22 3,229,673 1/1966 Ehrhardt ..418/123 PrimaryExaminer-Carlton R. Croyle Assistant Examiner-John J. Vrablik [57]ABSTRACT A mechanism to damp vibration and chatter in the rotor apexseals of rotary internal combustion engines, pumps, compressors andother devices of generally epitrochoidal motion.

5 Claims, 2 Drawing Figures PATENTEUHARZ 01975 G INVENTOR WILL/AM w.GILBERT ROTOR APEX SEAL DAMPING DEVICE The present invention relates toa new and improved apex seal for rotary engines, pumps and compressorsand, more specifically, to new and improved means to reduce vibrationand chatter in such seals.

In rotary internal combustion engines such as the Wankel type and otherpump and compressor apparatus of generally epitrochoidal motion themoving apex of the rotor is commonly sealed against the stationarycasing or cylinder peripheral wall by a floating seal bar of generallyrectangular cross section and having a rounded edge at the point ofcontact with the cylinder wall. The seal could be likened to a straightpiston ring. The bar is contained in a radial slot or groove in a linkblock located in the apex of the rotor. It is generally the same lengthas the link block and is sometimes chamfered at the ends to accomodatecorner pieces for sealing the rotor at the junctions of the cylinderperipheral and side walls.

The seal bar is free to move in and out of the slot in the link blockwhich accomodates it so as to adapt to any variations in clearancebetween the rotor apex and the stationary casing or cylinder and toadapt to normal surface roughness. The bar is held in position andagainst the casing normally by gas pressures and centrifugal force but alight spring is usually inserted between the bar and the bottom of theslot in the link block to ensure sealing during start-up of the machine.

To provide for reasonable manufacturing tolerances and variations inthermal expansion of parts, the cylinder or casing is made to a constantclearance configuration slightly larger than the true epitrochoidal pathtraversed by the rotor apex. The sliding seal bar closes this clearancegap. In theory, the seal bar does not move appreciably in or out of theslot in the link block which accomodates it as the rotor turns in thecasing, the clearance being ostensibly constant.

However, the cylinders or casings of these types of machines frequentlyhave shown chatter marks on them after they have been in service, andparticularly if there have been periods of overspeed, clearly indicatingthat the apex seal bar has been vibrating in and out of its slot andchattering against the cylinder wall. The result, of course, isincreased cylinder wear, seal leakage with attendant loss of compressionand efficiency, vibration and other obvious undesirable effects.

It is the object of this invention to provide a new and improved rotaryengine, pump or compressor apex seal mechanism which will eliminate theaforementioned undesirable chattering and associated problems of priorart constructions.

The foregoing object and advantages of the present invention will bestbe understood by reference to the following detailed description takenin conjunction with the drawings in which:

FIG. 1 is a cross-sectional view taken through a typical rotor apex sealof a rotary combustion engine at right angles to the engine shaft axisand constructed in accordance with the features of the presentinvention.

FIG. 2 is an exploded perspective view showing the parts of theconstruction of FIG. 1.

Referring to the drawings, 3 is the apex of a typical rotor, 4 istypical link block, 6 is an apex seal bar, is the groove or slot in 4which retains 6, 7 is the casing or cylinder wall against which seal bar6 slides and seals,

and 8 is a typical pressure spring which pushes seal bar 6 againstcasing or cylinder wall 7 during start-up. Engine rotation is clockwiseas shown. 9 is a binding roller slot oblong in cross-section and formedin link block 4 with its major transverse axis at an angle to theleading face of seal bar groove 5. Slot 9 intersects groove 5 as shown.

A binding roller 10 or plurality of rollers in axial alignment rollsloose in slot 9. When 10 rolls to the inboard portion of slot 9 itengages in scallops or serrations 11 on the leading face of seal bar 6and retards 6 from moving into or out of groove 5. When 10 rolls to theoutboard portion of slot 9 it disengages from serrations 11 and bar 6 isfree to move in groove 5. Oil hole 12 connects to the engine lubricatingsystem directly or indirectly and its function will be described later.

Rotor apex 3, and with it, link block 4 traverse a typical approximatelyepitrochoidal path during each revolution. They are, therefore,cyclically accelerated toward and away from the geometric center of theepitrochoidal path which is also on the center line of the engine shaft.Seal bar 6 is, during most of the rotor revolution, held tight in groove5 primarily by gas pressure being greater on one side of it than it ison the other. However, inherently there are instants when gas pressureson both sides of seal bar 6 are equal and the bar becomes a free body,free to slide in and out of groove 5, except as restricted by spring 8.If this condition occurs at a time when link block 4 and its seal bargroove 5 are accelerating toward the center, then bar 6 is held as aresult of centrifugal forces against the casing or cylinder wall 7,scaling is maintained and bar 6 does not move appreciably in or out ofgroove 5, except to adapt to the configuration of the cylinder wall.However, if this condition of equal pressures on both sides of bar 6occurs when link block 4 and its seal bar groove 5 are accelerating awayfrom the center, then seal bar 6 is momentarily forced into groove 5against spring 8 pressure and chatter would be initiated were it not forroller 10 in slot 9 which corrects the problem by retarding, or in factpreventing, the bar 6 from moving inwardly in groove 5, because roller10 is also a free body and at the same instant is forced to the inboardportion of slot 9 where it binds bar 6 and prevents it from movinginward. When the acceleration of 3 and 4 return to toward the center,roller 10 returns to the outboard portion of slot 9, disengages fromseal bar 6, and has no effect on the normal seal operation.

Oil hole 12 is supplied directly or indirectly from the enginelubrication system and communicates to slot 9 through holes or ports 13which enter 9 at the inboard flat of the slot as shown. Holes or ports14 connect the rounded end of slot 9 next to seal bar 6 to the spacepartially filled by spring 8 at the bottom of groove 5 in link block 4.When roller 10 is at the outboard portion of slot 9, lubricating oil maypass from hole 12 to slot 9. When roller 10 moves to the inboard portionof slot 9, it first covers ports 13 then forces oil through ports 14into the aforementioned space at the bottom of groove 5 partiallyoccupied by spring 8. The hydraulic oil pressure thus cyclicallyincreases and decreases so as always to assist the binding or unbindingaction of roller 10 against bar 6 to prevent undesirable inward motionof seal bar 6 in slot 5. The lubricating oil also serves to dampen themovement of spring 8 and to dampen the impact of roller on the ends ofslot 9 as it rolls back and forth. It should be noted that when therotor apex accelerates away from the engine center and roller 10 movestoward seal bar 6 at the inboard portion of slot 9, the lubricating oilin holes 13 is forced away from slot 9 and back to hole 12 and does notenter slot 9 outboard portion so as to block the return of roller 10 tothe outboard portion of slot 9 when the acceleration of the rotor apexreturns to toward engine center.

It should also be noted that roller 10 may also be a bar of rectangularor other cross-section so long as it slides back and forth in slot 10 inand out of contact with sealing bar 6 as the rotor apex acceleratestoward or away from the engine shaft centerline.

It should also be noted that the serrations or scallops 11 in seal bar 6may or may not be necessary to accomplish the desired binding action ofroller 10 into seal bar 6 to retard its inward motion at the desirableinstant. A flat or otherwise roughened surface may, in certain designs,accomplish the desired result.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. A rotor apex seal damping device for a radially movable apex sealbar, said bar being retained and guided in a radial seal bar slot in theapex of a rotating polygonal piston in a rotary internal combustionengine, compressor, pump or other machine in which the piston apex andseal bar traverse an epitrochoidal path and are accelerated alternatelyaway from and toward center of said engine and wherein said seal barslidably seals the piston apex to a stationary cylinder wall ofgenerally epitrochoidal configuration, said damping device consisting ofa binding means in axial alignment contained in and free to movelaterally in a guiding slot of generally oblong cross section, saidguiding slot being formed in the piston apex, the longitudinal axes ofthe guiding slot and binding means being parallel to the longitudinalaxis of said seal bar and the major transverse axis of the oblongguiding slot being set at an angle to the leading face of the seal barapproximately on the line of maximum piston apex acceleration away fromengine center with a portion of the guiding slot nearest the seal barintersecting the path of radial movement of the leading face of the sealbar, such that, at the time in the piston apex revolution itsacceleration is away from engine center and said binding means is forcedinward by centrifugal forces toward the portion of the guiding slotwhich intersects the leading face of the seal bar, the binding meansbinds tangentially into the seal bar and retards said bar from moving,and such that, at the time in the piston apex revolution itsacceleration is toward engine center and said binding means is forcedoutward by centrifugal forces to the portion of the guiding slot awayfrom the apex seal bar, said roller does not bind said apex seal bar.

2. The rotor apex seal damping device of claim 1 including spring meansin the seal bar slot urging the seal bar outwardly.

3. The rotor apex seal damping device of claim 1 wherein said bindingmeans is at least one cylindrical roller and said guiding slot is aroller slot.

4. The rotor apex seal damping device of claim 3 wherein at least aportion of the oblong roller slot adjacent to the seal bar slot containsa hydraulic fluid pressure medium and communicates through conduit meansto the space at the bottom of said seal bar slot,

and wherein said conduit means and said space also contain the hydraulicfluid pressure medium, so that when the roller moves inward, said fluidis compressed and the hydraulic fluid pressure against the bottom of theseal bar is increased, thus retarding radially inward motion of saidseal bar, and when the roller moves out ward, the hydraulic fluid isdecompressed and the hydraulic fluid pressure against the bottom of theseal bar is decreased, both movements resulting in the hydraulic fluidpressure under the seal bar being alternately increased and decreased atthe proper instants in the engine rotation so as to damp the radialmovements of said seal bar in and out of the seal bar slot.

5. The rotor apex seal damping device of claim 4 wherein the hydraulicfluid pressure medium is admitted to the oblong roller slot through atleast one port which is the terminus of a conduit means connecting to ahydraulic fluid source means, said port being located near or on thecenter of the longer inboard side of said roller slot and wherein whenthe roller is at either end of the roller slot, said port is not coveredby the roller and the roller slot communicates to said hydraulic fluidsource means, and wherein as said roller is passing from one end of theslot to the other end and over the port the roller closes said port andthe slot does not communicate to the hydraulic fluid source means.

i I i

1. A rotor apex seal damping device for a radially movable apex sealbar, said bar being retained and guided in a radial seal bar slot in theapex of a rotating polygonal piston in a rotary internal combustionengine, compressor, pump or other machine in which the piston apex andseal bar traverse an epitrochoidal path and are accelerated alternatelyaway from and toward center of said engine and wherein said seal barslidably seals the piston apex to a stationary cylinder wall ofgenerally epitrochoidal configuration, said damping device consisting ofa binding means in axial alignment contained in and free to movelaterally in a guiding slot of generally oblong cross section, saidguiding slot being formed in the piston apex, the longitudinal axes ofthe guiding slot and binding means being parallel to the longitudinalaxis of said seal bar and the major transverse axis of the oblongguiding slot being set at an angle to the leading face of the seal barapproximately on the line of maximum piston apex acceleration away fromengine center with a portion of the guiding slot nearest the seal barintersecting the path of radial movement of the leading face of the sealbar, such that, at the time in the piston apex revolution itsacceleration is away from engine center and said binding means is forcedinward by centrifugal forces toward the portion of the guiding slotwhich intersects the leading face of the seal bar, the binding meansbinds tangentially into the seal bar and retards said bar from moving,and such that, at the time in the piston apex revolution itsacceleration is toward engine center and said binding means is forcedoutward by centrifugal forces to the portion of the guiding slot awayfrom the apex seal bar, said roller does not bind said apex seal bar. 3.The rotor apex seal damping device of claim 1 wherein said binding meansis at least one cylindrical roller and said guiding slot is a rollerslot.
 3. The rotor apex seal damping device of claim 1 including springmeans in the seal bar slot urging the seal bar outwardly.
 4. The rotorapex seal damping device of claim 3 wherein at least a portion of theoblong roller slot adjacent to the seal bar slot contains a hydraulicfluid pressure medium and communicates through conduit means to thespace at the bottom of said seal bar slot, and wherein said conduitmeans and said space also contain the hydraulic fluid pressure medium,so that when the roller moves inward, said fluid is compressed and thehydraulic fluid pressure against the bottom of the seal bar isincreased, thus retarding radially inward motion of said seal bar, andwhen the roller moves outward, the hydraulic fluid is decompressed andthe hydraulic fluid pressure against the bottom of the seal bar isdecreased, both movements resulting in the hydraulic fluid pressureunder the seal bar being alternately increased and decreased at theproper instants in the engine rotation so as to damp the radialmovements of said seal bar in and out of the seal bar slot.
 5. The rotorapex seal damping device of claim 4 wherein the hydraulic fluid pressuremedium is admitted to the oblong roller slot through at least one portwhich is the terminus of a conduit means connecTing to a hydraulic fluidsource means, said port being located near or on the center of thelonger inboard side of said roller slot and wherein when the roller isat either end of the roller slot, said port is not covered by the rollerand the roller slot communicates to said hydraulic fluid source means,and wherein as said roller is passing from one end of the slot to theother end and over the port the roller closes said port and the slotdoes not communicate to the hydraulic fluid source means.